This invention relates generally to power generation systems and, more particularly, to a system and assemblies for pre-heating fuel in a combined cycle power plant.
At least some known power generation systems include a multi-stage heat recovery steam generator (HRSG) configured to generate progressively lower grade steam from each successive stage in the exhaust of a gas turbine engine. Relatively high grade heat at a gas inlet to the HRSG is capable of generating relatively high pressure steam in a high pressure stage or section of the HRSG. After heat is removed from the gas in the high pressure stage the gas is channeled to an intermediate pressure stage where the relatively cooler gas is only capable of generating a relatively lower pressure or intermediate pressure steam.
To increase the efficiency of the combustion in the gas turbine engine the fuel typically preheated. The preheating of the fuel uses one or more water flows from respective HRSG sections to heat the fuel in a multi-stage fuel heater. However, the amount of heat addition to the fuel using the multistage fuel heater is limited.